Diego, I believe that the internet is the #1 reason some of these cars have surfaced, and it's definately driven the prices up on some cars. Bigger audience, more people willing to buy, and that tends to send people out into junkyards looking for rare cars, maybe cars with tree trunks growing out of the hood, but these people are armed with info taken from websites, and they're looking for codes.
I don't think a stripped RAIV GTO is incredibly rare either, but you had said a few posts ago, "Where did you get the information you could order a GTO gutted? Have you seen one before?"
I guess the term "oddball" would be based on the percentage of the total # of units made of a particular car. For instance, I would consider the red 71 Judge ragtop as "oddball", but not an anomoly. They only made 17 in total, so it's a rare color of a rare car.
An anomoly may be that white with red top/red interior 70 GTO from a while ago, or that one-off red 72 Trans Am, or a vinyl top on a 69 Trans Am.
You're right though, the term "oddball" is often misused to describe a car that really isn't that odd, just a little out of the ordinary.